JP2008215951A - Radiation detector - Google Patents

Abstract

It is possible to prevent moisture from entering the scintillator layer, suppress deterioration of the scintillator layer in an accelerated test under a high temperature and high humidity condition, and efficiently radiate visible light generated in the scintillator layer to a photoelectric conversion element. An indirect radiation detector is provided.
A transparent substrate, a plurality of thin film transistors and a plurality of storage capacitors provided on the transparent substrate, an insulating layer formed on the transparent substrate including the thin film transistors and the storage capacitors, and the thin film transistors, respectively. An electrode substrate having a plurality of photoelectric conversion elements that are connected and convert visible light into an electrical signal; a scintillator layer that is formed on the electrode substrate and converts radiation into visible light; and at least a scintillator layer that is highly thermoplastic. A reflective film layer containing 70% by weight or more of titanium oxide powder in the molecular compound, an adhesive layer formed on the surface of the electrode substrate including the reflective film layer, and water adhered at 40 ° C. and 90 RH A protective layer having a moisture-proof layer having a transmittance of 0.5 g / m ² / day or less.
[Selection] Figure 1

Description

  The present invention relates to a radiation detector that converts incident radiation into an electrical signal.

  As a new generation X-ray diagnostic image detector, an active matrix type flat detector has been developed. By detecting irradiated X-rays in this flat detector, an X-ray image or a real-time X-ray image is output as a digital signal.

  There are two types of flat detectors of this type: a direct method and an indirect method. The direct method is a method of acquiring an image by converting X-rays directly into a charge signal by an X-ray conversion film. On the other hand, in the indirect method, X-rays are changed to visible light by a scintillator layer, and then the visible light is converted into a charge signal by a photoelectric conversion element such as an amorphous silicon (a-Si) photodiode or CCD to acquire an image. It is a method to do.

The use of materials such as amorphous selenium (a-Se), lead iodide (PbI ₂ ), mercury iodide (HgI ₂ ) has been studied as an X-ray conversion film used for a direct-type flat panel detector. Yes. Since this X-ray conversion film converts X-rays directly into a charge signal, an image with good resolution characteristics can be acquired. However, when this X-ray conversion film is left in an air atmosphere, the material deteriorates due to the influence of moisture, and the sensitivity characteristics and resolution characteristics deteriorate.

As a scintillator layer used for an indirect type flat panel detector, cesium iodide: sodium (CsI: Na), cesium iodide: thallium (CsI: Tl), sodium iodide (NaI), gadolinium oxysulfide (Gd) Materials such as ₂ O ₂ S) are used. The scintillator layer is improved in resolution characteristics by forming a groove by dicing or the like, or by depositing it on a columnar structure, or by providing the columnar structure. However, many materials used for the scintillator layer exhibit strong hygroscopicity, and sensitivity characteristics and resolution characteristics deteriorate when left in an air atmosphere.

For this reason, in order to prevent the deterioration of the characteristics of the X-ray conversion film used for the direct type flat detector and the scintillator layer used for the indirect type flat detector, it has shielding properties against the atmosphere and moisture and transmits X-rays. It is considered to provide a protective layer having properties. Patent Document 1 discloses that an organic film such as a xylylene-based resin formed by an evaporation deposition method in a vacuum or an inert gas atmosphere is used as a protective layer. Patent Document 2 discloses the use of an inorganic film such as silicon oxynitride as a protective layer.
Japanese Examined Patent Publication No. 5-39558 (page 2-3, FIG. 1 and FIG. 3) Japanese Examined Patent Publication No. 6-58440 (page 2-5, Fig. 1)

  However, the protective layer obtained by the evaporation deposition method described in Patent Document 1 requires a long time for film formation. An expensive vapor deposition apparatus is required. In addition, the resin structure is rigid, the adhesive strength with the substrate is weak, and there is a risk of peeling due to a difference in thermal expansion. Due to the weak adhesive force between the resin protective layer and the substrate, the moisture permeability increases at the edge of the protective layer, making it difficult to suppress deterioration of sensitivity characteristics and resolution characteristics for a long time. Furthermore, the protective layer made of an organic film has few defects such as pinholes immediately after formation, and has a characteristic that cracks are hardly generated even in a thin film. However, since a heating process exceeding the glass transition temperature (Tg) of the organic film is added in the assembly of the X-ray detector, defects such as pinholes may occur due to softening and modification of the organic film, which may increase the moisture permeability. There is.

  On the other hand, the protective layer made of an inorganic film described in Patent Document 2 has a high glass transition temperature (Tg), so there is no defect due to the heating process, but cracks occur because the mechanical strength of the thin film is small. easy.

  On the other hand, in the vapor deposition method using an organic substance, the refractive index ratio between the columnar crystal and the gap is close to 1 due to the resin entering the gap between the columnar crystals on the substrate side, and the reflection efficiency in the columnar crystal is reduced. It becomes difficult to obtain high sensitivity characteristics and resolution characteristics that are stable for a long period of time.

  The present invention prevents moisture from entering the scintillator layer, suppresses deterioration of the scintillator layer in an accelerated test under a high temperature and high humidity condition, and can efficiently emit visible light generated in the scintillator layer to the photoelectric conversion element. And an indirect radiation detector.

According to the first aspect of the present invention, a transparent substrate, a plurality of thin film transistors and a plurality of storage capacitors provided on the transparent substrate, an insulating layer formed on the transparent substrate including the thin film transistors and the storage capacitors, An electrode substrate connected to each of the thin film transistors and having a plurality of photoelectric conversion elements for converting visible light into electrical signals;
A scintillator layer formed on the electrode substrate for converting radiation into visible light; and a reflective film layer formed on at least the scintillator layer and containing 70% by weight or more of titanium oxide powder in a thermoplastic polymer compound; A protective layer having an adhesive layer formed on the surface of the electrode substrate including a film layer, and a moisture-proof layer adhered to the adhesive layer and having a moisture permeability of 0.5 g / m ² / day or less at 40 ° C. and 90 RH;
A radiation detector is provided.

According to a second aspect of the present invention, a transparent substrate, a plurality of thin film transistors and a plurality of storage capacitors provided on the transparent substrate, an insulating layer formed on the transparent substrate including the thin film transistors and the storage capacitors, An electrode substrate connected to each of the thin film transistors and having a plurality of photoelectric conversion elements for converting visible light into electrical signals;
A scintillator layer formed on the electrode substrate for converting radiation into visible light; and a reflective film layer formed on at least the scintillator layer and containing 70% by weight or more of titanium oxide powder in a thermoplastic polymer compound; and the electrode substrate A frame-like adhesive layer located on the surface and the side of the scintillator layer and adhered to the reflective film layer, and adhered onto the frame-like adhesive layer, and moisture permeability at 40 ° C. and 90 RH is 0.5 g / m ² / a protective layer having a moisture-proof layer of day or less;
A radiation detector is provided.

According to a third aspect of the present invention, a transparent substrate, a plurality of thin film transistors and a plurality of storage capacitors provided on the transparent substrate, an insulating layer formed on the transparent substrate including the thin film transistors and the storage capacitors, An electrode substrate connected to each of the thin film transistors and having a plurality of photoelectric conversion elements for converting visible light into electrical signals;
A scintillator layer that is formed on the electrode substrate and converts radiation into visible light; and an adhesive layer that is bonded to the electrode substrate including the scintillator layer; and a titanium oxide that is bonded to the adhesive layer and is formed on the thermoplastic polymer compound. A protective layer having a reflective film layer containing 70% by weight or more of a powder and a moisture-proof layer laminated on the reflective film layer and having a moisture permeability of 0.5 g / m ² / day or less at 40 ° C. and 90 RH;
A radiation detector is provided.

According to a fourth aspect of the present invention, a transparent substrate, a plurality of thin film transistors and a plurality of storage capacitors provided on the transparent substrate, an insulating layer formed on the transparent substrate including the thin film transistors and the storage capacitors, An electrode substrate connected to each of the thin film transistors and having a plurality of photoelectric conversion elements for converting visible light into electrical signals;
A scintillator layer that is formed on the electrode substrate and converts radiation into visible light; and a frame-like adhesive layer that is bonded to the electrode substrate surface and the side surface of the scintillator layer; A reflective film layer containing 70% by weight or more of titanium oxide powder in a polymer compound; a moisture-proof layer laminated on the reflective film layer and having a moisture permeability of 0.5 g / m ² / day or less at 40 ° C. and 90 RH; A protective layer having:
A radiation detector is provided.

  According to the present invention, moisture penetration into the scintillator layer is prevented, deterioration of the scintillator layer in an accelerated test under a high temperature and high humidity condition is suppressed, and visible light generated in the scintillator layer is efficiently emitted to the photoelectric conversion element. It is possible to provide a radiation detector capable of stably maintaining high sensitivity characteristics and resolution characteristics over a long period of time.

  Hereinafter, a radiation detector according to an embodiment of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a cross-sectional view of an essential part showing an indirect conversion type X-ray detector that is a radiation detector according to the first embodiment, and FIG. 2 is a schematic cross-sectional view showing a protective layer forming step of the X-ray detector of FIG. FIG.

  The indirect conversion type X-ray detector 1 includes an active matrix light conversion substrate 2 which is an electrode substrate. The photoelectric conversion substrate 2 includes a translucent substrate (glass substrate) 3 made of, for example, Corning Corporation product name: Corning 1737, and a plurality of switching elements as a matrix formed on one main surface of the glass substrate 3. The thin film transistor 4 and a plurality of rectangular flat storage capacitors 5, an insulating layer (flattening resin layer) 6 formed on the thin film transistors 4 and the storage capacitor 5, and the thin film transistor 4 connected to the flattening resin layer 6 And a photoelectric conversion element that converts visible light into an electrical signal, for example, a photodiode 7.

  The thin film transistor 4 has a gate electrode 11 formed on the glass plate 3, and the storage capacitor 5 has a first electrode 12 formed on the glass plate 3. An insulating film 13 serving as a gate insulating film and a dielectric film is formed on the entire surface of the glass plate 3 including the electrodes 11 and 12. For example, the active layer 14 made of impurity-doped polycrystalline silicon is formed on the insulating film 13 so as to face the gate electrode 11. The second electrode 15 made of impurity-doped polycrystalline silicon is formed on the insulating film 13 so as to face the first electrode 12. The source electrode 16 is formed on the insulating film 13 so as to overlap one end portion (for example, the left end portion) of the active layer 14. The drain electrode 17 is formed on the insulating film 13 so as to overlap the other end portion (for example, the right end portion) of the active layer 14 and one end (for example, the left end portion) of the second electrode 15. The planarizing resin layer 6 is formed on the entire surface of the insulating film 13 including the active layer 14, the second electrode 15, the source electrode 16 and the drain electrode 17.

  The photodiode 7 is formed on the planarizing resin layer 6 for each pixel as an amorphous silicon (a-Si) pn diode structure or a pin diode structure. The photodiode 7 has a current collecting electrode 21 as a first electrode and a bias electrode 22 made of, for example, ITO (Indium-Tin Oxide) as a second electrode. The collecting electrode 21 is connected to the drain electrode 17 through the through hole 23 of the planarizing resin layer 6. The bias electrode 22 forms a bias electric field between the collecting electrodes 21 by applying a bias voltage. An insulating resin layer 24 is formed on the planarizing resin layer 6 excluding the photodiode 7, the collecting electrode 21, and the bias electrode 22 so as to be flush with the bias electrode 22.

  On one side edge along the row direction on the surface of the glass substrate 3, there is a high-speed signal processing unit (not shown) in the form of an elongated rectangular plate that controls the operation state of each thin film transistor 4, for example, on and off of each thin film transistor 4. It is attached. The high-speed signal processing unit is a line driver for controlling signal reading and processing the read signal. One end of a plurality of control lines (not shown) is electrically connected to the high-speed signal processing unit. Each control line is wired along the row direction of the glass substrate 3 so as to be positioned between the pixels. Each control line is electrically connected to the gate electrode 11 of the thin film transistor 4 constituting each pixel in the same row.

  On the surface of the glass substrate 3, a plurality of data lines (not shown) are wired along the column direction so as to be positioned between the pixels. Each data line is electrically connected to the source electrode 16 of the thin film transistor 4 constituting the pixel in the same column, and receives an image data signal from the thin film transistor 4 constituting the pixel in the same column. One end of each data line is electrically connected to a high-speed signal processing unit, and the high-speed signal processing unit is electrically connected to a digital image transmission unit (not shown) as a digital image processing unit. The digital image transmission unit is attached in a state of being led out of the photoelectric conversion substrate 2.

  A scintillator layer 31 that converts incident X-rays into visible light is formed on an insulating resin layer 24 including a bias electrode 22. The scintillator layer 31 is configured by depositing phosphors such as sodium iodide (NaI) and cesium iodide (CsI) on the individual columnar structures 31a by a method such as vapor deposition, electrobeam, or sputtering. Columnar crystals. Therefore, the scintillator layer 31 has a low resolution with a small diffusion of light generated by the columnar crystals.

The protective layer 41 having a shielding property against the air and moisture and a permeability to X-rays is formed on the surface of the photoelectric conversion substrate 2 including the surface and side surfaces of the scintillator layer 31. The protective layer 41 includes a reflective film layer 42 containing 70% by weight or more of titanium oxide powder in a thermoplastic polymer compound formed on the surface and side surfaces of the scintillator layer 31, and an adhesive layer bonded to the reflective film layer 42. 43 and a moisture-proof layer 44 having a moisture permeability of 0.5 g / m ² / day or less at 40 ° C. and 90 RH laminated on the adhesive layer 43.

  For example, as shown in FIG. 2, the protective layer 41 is formed by applying a coating for a reflective film containing 70% by weight or more of titanium oxide powder to a thermoplastic polymer compound on the surface and side surfaces of the scintillator layer 31 in advance. The layer 42 is formed, and the moisture-proof layer 44 having the adhesive layer 43 on one surface is adhered to the surface of the photoelectric conversion substrate 2 including the reflective film layer 42 via the adhesive layer 43.

  The reflective film layer 42, the adhesive layer 43, and the moisture-proof layer 44 constituting the protective layer 41 will be described in detail below.

(Reflective film layer)
The reflective film layer plays a role of reflecting visible light generated by the incidence of radiation (for example, X-rays) to the scintillator layer 31 toward the photodiode 7, and 70 wt% of titanium oxide powder is added to the thermoplastic polymer compound. It has the composition containing above. Here, although titanium oxide powder transmits without absorbing or reflecting radiation (for example, X-rays), the titanium oxide powder does not absorb visible light generated by incidence of radiation (for example, X-rays) to the scintillator layer 31. Functions as a reflective material to reflect. That is, the protective layer 41 having the reflective film layer 42 containing titanium oxide powder exhibits high transparency to radiation (for example, X-rays).

  As the thermoplastic polymer compound, for example, butyral resin, polyester resin, acrylic resin, styrene resin, silicone resin, epoxy resin and the like can be used.

  The titanium oxide powder preferably has an average diameter of 0.1 to 1 μm. The titanium oxide powder is preferably subjected to a surface treatment using alumina, alumina and an organic substance in order to prevent deterioration of the thermoplastic polymer compound.

  When the content of the titanium oxide powder in the thermoplastic polymer compound is less than 70% by weight, the reflectivity to visible light may be reduced. The upper limit of the content of titanium oxide powder is preferably 95% by weight or less in consideration of adhesion (adhesiveness) to the scintillator layer 31.

  The reflective film layer preferably has a thickness of 50 to 800 μm.

  In order to prepare a coating for a reflective film for forming the reflective film layer, for example, a thermoplastic polymer compound is dissolved in a solvent, and a predetermined amount of titanium oxide powder is added to the solution, followed by a revolving mixing. A method of pre-mixing with a machine or the like and further uniformly dispersing using a homogenizer, three rolls, sand mill or the like is employed.

(Adhesive layer)
A general adhesive agent and an adhesive can be used for the adhesive layer. Specifically, acrylic adhesives, silicone adhesives, vinyl acetate adhesives, etc. use rubber adhesives, epoxy resin adhesives, phenol resin adhesives, polyimide resin adhesives, etc. can do. In particular, in consideration of large X-ray detectors, an adhesive layer is formed from an adhesive or pressure sensitive adhesive having a low elastic modulus, for example, an acrylic pressure sensitive adhesive, a silicone pressure sensitive adhesive, or a butyl rubber based pressure sensitive adhesive at room temperature. Is preferred.

  In the adhesive layer, in order to prevent moisture from entering from the edges, the resin component is adjusted for moisture shielding and coefficient of thermal expansion, and in order to improve the coating properties, it is crushed, spherical, subspherical, flakes It is also possible to add a fibrous inorganic component (in particular, a spherical or subspherical inorganic component having an average particle diameter of 10 μm or less in consideration of surface smoothness) or a fibrous inorganic component for the purpose of reinforcing crack resistance. is there.

  Examples of inorganic components such as crushed materials include fused silica, crystalline silica, glass, talc, alumina, calcium silicate, calcium carbonate, barium sulfate, magnesia, silicon nitride, boron nitride, aluminum nitride, magnesium oxide, beryllium oxide, Mica is used. Of these inorganic components, fused silica or crystalline silica is particularly preferable.

  Examples of fibrous inorganic components include titania, aluminum borate, silicon carbide, silicon nitride, potassium titanate, basic magnesium, zinc oxide, graphite, magnesia, calcium sulfate, magnesium borate, titanium diboride, α- Whiskers such as alumina, chrysotile, wollastonite, or amorphous fibers such as E glass fiber, silica alumina fiber, silica glass fiber, Tyranno fiber, silicon carbide fiber, zirconia fiber, γ alumina fiber, α-alumina fiber, Crystalline fibers such as PAN-based carbon fibers and pitch-based carbon fibers can be used. Of these fibrous inorganic components, those having an average fiber diameter of 5 μm or less and a maximum fiber length of 10 μm or less are preferable from the viewpoint of the uniformity of the coating film surface.

  The inorganic component is preferably blended in the range of 0.1 to 50% by weight with respect to the total amount of the resin component and the inorganic component. When the blending amount of the inorganic component is less than 0.1% by weight, the thermal expansion coefficient of the adhesive layer increases, and there is a possibility that improvement in thermal shock resistance cannot be expected. On the other hand, when the blending amount of the inorganic component exceeds 50% by weight, the fluidity of the adhesive layer becomes insufficient, the workability decreases, and voids are generated, thereby forming a protective layer with a uniform thickness. It becomes difficult.

  In the case of an adhesive layer using a resin component having a high elastic modulus, a thermoplastic resin, a rubber component, various oligomers, and the like are added in order to improve crack resistance when the X-ray detector is subjected to a thermal cycle. It is possible to lower the elastic modulus. Examples of the thermoplastic resin may be modified with butyral resin, polyamide resin, aromatic polyester resin, phenoxy resin, MBS resin, ABS resin, silicone oil, silicone resin, silicone rubber, fluororubber, or the like.

  Various plastic powders, various engineering plastic powders, and the like can be further added to the adhesive layer. In addition, the adhesive layer has an adhesion-imparting agent to further improve the adhesion, water repellent, oil repellent, insect repellent, ultraviolet absorber, antibacterial agent, antistatic agent, paint fixing agent, anti-wrinkle agent, oxidation An inhibitor, a surfactant, a coupling agent, a colorant and the like can be added and blended.

  To add inorganic components to the resin component, add the inorganic component to the resin component, add solvent as necessary, three rolls, ball mill, sand mill, rakai machine, homogenizer, self-revolving mixer, universal A method of uniformly mixing using a mixer, an extruder, a Henschel mixer, or the like can be employed.

(Dampproof layer)
The moisture-proof layer has a characteristic of moisture permeability of 0.5 g / m ² / day or less at 40 ° C. and 90 RH, and for example, an inorganic vapor deposited resin film can be used.

  As the film substrate, for example, thermoplastic resins such as polyethylene terephthalate, polyethylene, polypropylene, PVA, and PCTFE are preferable, and an alloyed one can also be used.

As the inorganic deposition layer, for example, silicon dioxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), and silicon nitride (Si ₃ N ₄ ) are preferable.

  Specific inorganic vapor-deposited resin films include V, P2, H, T, TZ, NY, NR, and S (all trade names made by Mitsubishi Plastics), GL, which are tech barrier films formed with a silica vapor-deposited film. GL-AU, GL-AE, GL-AEH, GL-AEY, GL-AEO, alumina-deposited GX film GX (all trade names manufactured by Toppan Printing Co., Ltd.), and GL film-silica-deposited film GL-E (trade name, manufactured by Toppan Printing Co., Ltd.) and the like.

  The moisture-proof layer can be used by multilayering the inorganic deposited resin film.

  It is preferable that the moisture-proof layer has a thickness of 10 to 500 μm.

  As the method for forming the multilayer film, for example, the adhesive is applied to the moisture-proof layer by a screen printing method, a metal screen printing method, a dispensing method, a pressure bonding method, dipping, brush coating, roller coating, flow coating, various spray coatings, a die coater, A method of drying the coating film after applying with a knife coater, spin coater, curtain flow coater, reverse coater or the like can be employed. As a method for drying the coating film, natural drying, ventilation drying, heat drying, vacuum drying, drying using microwaves, and drying using ultrasonic waves can be used.

  Next, the operation of the X-ray detector according to the first embodiment will be described.

  First, when X-rays enter the scintillator layer 31 through the protective layer 41, visible light is generated in the scintillator layer 31. Visible light is emitted toward the protective layer 41 and the photodiode 7. Since the protective layer 41 has a reflective film layer 42 containing 70 wt% or more of titanium oxide powder in a thermoplastic polymer compound, visible light is reflected by the reflective film layer 42 and emitted toward the photodiode 7. The Visible light is photoelectrically converted by the photodiode 7. At this time, by applying a bias voltage to the upper bias electrode 22 across the photodiode 7 to generate a bias electric field at the collecting electrode 21, charges (signal charges) generated in the photodiode 7 are collected. It moves to the electrode 21 and is stored in the storage capacitor 5 from the collecting electrode 21 through the drain electrode 17 and the like.

  On the other hand, the signal charges stored in the storage capacitor 5 are sequentially controlled and read out for each row, for example, by a high-speed signal processing unit (not shown).

  That is, an ON signal of, for example, 10 V is input from the high-speed signal processing unit to the pixel-unit gate electrode 11 located in the first row through a data line (not shown) to turn on the pixel-unit thin film transistors 4 in the first row. Put it in a state. The signal charge stored in the storage capacitor 5 in the pixel unit in the first row when the thin film transistor 4 is turned on is output from the drain electrode 17 to the source electrode 16 as an electrical signal. The electric signals output to the source electrode 16 are each amplified by the high-speed signal processing unit. The amplified electrical signal is output to a digital image transmission unit (not shown), converted into a serial signal, further converted into a digital signal, and sent to a signal processing circuit (not shown).

  When the readout of the charge of the storage capacitor 5 in the pixel unit located in the first row is completed, an off signal of, for example, −5 V is supplied from the high-speed signal processing unit to the pixel-unit gate electrode 11 in the first row through the data line. Is input to turn off the thin film transistors 4 in the pixel units in the first row.

  Thereafter, the above-described operation is sequentially performed for the pixel units in the second row and thereafter. The signal charges stored in the storage capacitors 5 for all pixels are read out, sequentially converted into digital signals and output, and an electrical signal corresponding to one X-ray screen is output from a digital image transmission unit (not shown). .

As described above, according to the first embodiment, on the electrode substrate (light conversion substrate) 2 including the scintillator layer 31 of the X-ray detector 1, the reflective film layer 42, the adhesive layer 43, and moisture at 40 ° C. and 90 RH. By providing the protective layer 41 in which the moisture-proof layer 44 having excellent moisture-proof performance with a transmittance of 0.5 g / m ² / day or less is laminated in this order, it is possible to suppress moisture intrusion into the scintillator layer 31. Become. In particular, the reflective film layer 42 is formed on the surface and side surfaces of the scintillator layer 31, and the adhesive layer 43 is formed from the reflective film layer 42 to the surface of the light conversion substrate 2, whereby the scintillator is formed from the side surface of the protective layer 41. Intrusion of moisture toward the layer 31 can be suppressed. In addition, by using an acrylic pressure-sensitive adhesive, a silicone pressure-sensitive adhesive or a butyl rubber-based pressure-sensitive adhesive that exhibits adhesiveness at room temperature as the adhesive layer 43, stable adhesiveness to the light conversion substrate 2 is exhibited, and from the end side surface. Intrusion of moisture toward the scintillator layer 31 can be more reliably suppressed.

  Further, since visible light generated in the scintillator layer 31 on which X-rays are incident can be reflected toward the photodiode 7 by the reflective film layer 42 containing 70% by weight or more of titanium oxide powder in a thermoplastic polymer compound, The photoelectric conversion efficiency in the diode 7 can be improved.

  Furthermore, the reflective film layer 42 has a composition containing 70% by weight or more of titanium oxide powder in a thermoplastic polymer compound, and can be formed on the scintillator layer 31 by, for example, a simple coating method. Thereafter, the multilayered film of the adhesive layer 43 and the moisture-proof layer 44 is laminated and adhered to the reflective film layer 42, whereby the protective layer 41 having a three-layer structure can be formed. As a result, the protective layer 41 having the reflective film layer 42 and having no defects such as pinholes can be formed without requiring a large-scale facility as in the case of using a conventional deposited film as the reflective layer.

  Accordingly, it is possible to prevent moisture from entering the scintillator layer 31, suppress degradation of the scintillator layer 31 in an accelerated test under a high temperature and high humidity condition and prevent a decrease in resolution and light emission efficiency, and photoelectrically generate visible light generated in the scintillator layer 31. An X-ray detector capable of maintaining high sensitivity characteristics and resolution characteristics over a long period of time because the photoelectric conversion efficiency of the photodiode 7 can be improved by efficiently radiating it to the conversion element (photodiode) 7. Can be provided.

(Second Embodiment)
FIG. 3 is a schematic cross-sectional view showing a process of forming a protective layer on the scintillator layer in the radiation detector (for example, X-ray detector) according to the second embodiment. In FIG. 3, the same members as those in FIGS. 1 and 2 described above are denoted by the same reference numerals, and the description thereof is omitted.

In the second embodiment, a reflective film coating material containing 70 wt% or more of a titanium oxide powder in a thermoplastic polymer compound is applied in advance on an electrode substrate (light conversion substrate) 2 including a scintillator layer 31 to form a reflective film layer 42. And having a frame-like adhesive layer 45 around one surface on the electrode substrate (light conversion substrate) 2 including the reflective film layer 42 and having a moisture permeability of 0.5 g / m at 40 ° C. and 90 RH. ^The protective layer is formed by adhering the moisture-proof layer 44 of ² / day or less so that the frame-like adhesive layer 45 is positioned on the side surface of the scintillator layer 31 including the reflective film layer 42 and the surface of the light conversion substrate 2.

  According to the second embodiment, the end of the protective layer is formed by forming the moisture-proof layer 44 on the light conversion substrate 2 including the scintillator layer 31 covered with the reflective film layer 42 using the frame-shaped adhesive layer 45. The intrusion of moisture from the side surface toward the scintillator layer 31 can be more reliably suppressed as compared with the protective layer of the first embodiment described above. Therefore, it is possible to suppress degradation of the scintillator layer 31 for a longer period in an accelerated test under a high temperature and high humidity condition, and it is possible to maintain high sensitivity characteristics and resolution characteristics for a longer period of time. A line detector can be provided.

(Third embodiment)
FIG. 4 is a schematic cross-sectional view showing a process of forming a protective layer on the scintillator layer in the radiation detector (for example, X-ray detector) according to the third embodiment. In FIG. 4, the same members as those shown in FIGS.

In the third embodiment, the adhesive layer 43 and the reflective polymer layer 42 containing 70% by weight or more of the titanium oxide powder in the thermoplastic polymer compound and the water permeability at 40 ° C. and 90 RH are 0.5 g / m ² / day or less. The multilayered resin film 46 formed of the moisture-proof layer 44 is adhered to the electrode substrate (light conversion substrate) 2 including the scintillator layer 31 to form a protective layer. The adhesion of the multilayer resin film 46 is preferably performed under reduced pressure.

  According to the third embodiment, moisture penetration into the scintillator layer 31 can be prevented by the moisture-proof layer 44, and the multilayered resin film 46 is placed on the electrode substrate (light conversion substrate) 2 including the photoconductive layer 31. By adhering via the adhesive layer 43, a protective layer can be formed more easily than in the first embodiment described above, which can contribute to an improvement in productivity.

(Fourth embodiment)
FIG. 5 is a schematic cross-sectional view showing a process of forming a protective layer on the scintillator layer in the radiation detector (for example, X-ray detector) according to the fourth embodiment. In FIG. 5, the same members as those in FIGS. 1 and 2 described above are denoted by the same reference numerals, and the description thereof is omitted.

The fourth embodiment has a frame-like adhesive layer 45 around one surface on an electrode substrate (light conversion substrate) 2 including a scintillator layer 31, and titanium oxide powder is added to a thermoplastic polymer compound by 70 wt% or more. The frame-shaped adhesive layer 45 is formed on the surface of the electrode substrate 2 and includes a reflective film layer 42 and a moisture-proof layer 44 laminated on the reflective film layer 42 and having a moisture permeability of 0.5 g / m ² / day or less at 40 ° C. and 90 RH. The protective layer is formed by bonding so as to be located on the side surface of the scintillator layer 31.

  According to the fourth embodiment, by forming the multilayered reflective film layer 42 and the moisture-proof layer 44 on the light conversion substrate 2 including the scintillator layer 31 using the frame-shaped adhesive layer 45, the end of the protective layer is formed. Intrusion of moisture from the side surface toward the scintillator layer 31 can be prevented more reliably than the protective layer having the structure shown in FIG. Therefore, it is possible to suppress degradation of the scintillator layer 31 for a longer period in an accelerated test under a high temperature and high humidity condition, and it is possible to maintain high sensitivity characteristics and resolution characteristics for a longer period of time. A line detector can be provided.

  In the fourth embodiment, as shown in FIG. 6, the moisture-proof layer 44 may be laminated on the outer surface of the frame-like adhesive layer 45 as well as the reflective film layer 42 to form a protective layer. According to such a configuration, since the moisture-proof layer 44 is also laminated on the outer surface of the frame-like adhesive layer 45, moisture intrusion into the scintillator layer 31 can be more reliably performed than the protective layer shown in FIG. It becomes possible to suppress.

  In the second to fourth embodiments described above, the stress concentration by the adhesive layer 43 in direct contact with the scintillator layer 31 is reduced by reducing the elastic modulus of the adhesive layer 43 (or frame-like adhesive layer 45) in direct contact with the scintillator layer 31. Can be relaxed, a stable adhesive force can be maintained for a long period of time, and a large glass substrate 3 can be used.

  Hereinafter, embodiments of the present invention will be described in detail.

(Example 1)
90% by weight of titanium oxide powder with an average particle size of 0.25 μm and 10% by weight of butyral resin (trade name manufactured by Sekisui Chemical Co., Ltd .; ESREC BMS) are mixed together with cyclohexanone using a revolving mixer and then uniformly dispersed using a homogenizer. The coating for reflecting film was prepared in advance.

  Next, a CsI conversion film layer (scintillator layer) having a thickness of 600 μm was formed on a glass substrate made of Corning Corporation trade name: Corning 1737. Subsequently, the reflective film paint was applied to the surface and side surfaces of the scintillator layer using a dispenser and dried to form a reflective film layer having a thickness of 100 μm. Subsequently, an acrylic double-sided pressure-sensitive adhesive (trade name, manufactured by Soken Chemical Co., Ltd .; S-0679) with a thickness of 0.6 mm is adhered to one side of a moisture-proof layer (trade name, manufactured by Toppan Printing Co .; The multilayered resin film thus prepared was attached to the surface of the glass substrate including the reflective film layer to produce a protective layer.

(Example 2)
90% by weight of titanium oxide powder with an average particle size of 0.25 μm and 10% by weight of butyral resin (trade name manufactured by Sekisui Chemical Co., Ltd .; ESREC BMS) are mixed together with cyclohexanone using a revolving mixer and then uniformly dispersed using a homogenizer. The coating for reflecting film was prepared in advance.

  A CsI conversion film layer (scintillator layer) having a thickness of 600 μm was formed on a glass substrate made of Corning Corporation product name: Corning 1737. Subsequently, the reflective film paint was applied to the surface and side surfaces of the scintillator layer using a dispenser and dried to form a reflective film layer having a thickness of 100 μm. Subsequently, an acrylic double-sided adhesive (trade name, manufactured by Soken Chemical Co., Ltd .; S-0779) having a thickness of 0.7 mm is formed in a frame shape on the periphery of one side of a moisture-proof layer (trade name, manufactured by Toppan Printing Co .; The protective layer was prepared by adhering and pasting on the surface of the glass substrate including the reflective film layer via the frame-shaped adhesive layer.

(Example 3)
After mixing 80% by weight of titanium oxide powder having an average particle size of 0.2 μm and 20% by weight of butyral resin (trade name of Sekisui Chemical Co., Ltd .; ESREC BMS) together with cyclohexanone, the mixture is uniformly dispersed using a homogenizer. The coating for reflecting film was prepared in advance. Subsequently, the reflective coating material was applied to one side of an 80 μm thick moisture-proof layer (trade name, manufactured by Toppan Printing Co., Ltd .; GX film) using a bar coater and dried to a thickness of 100 μm. The reflective film layer was formed. Subsequently, a multilayer resin film in which a 0.7 mm-thick acrylic double-sided pressure-sensitive adhesive (trade name; S-0779, manufactured by Soken Chemical Co., Ltd.) was adhered as an adhesive layer to the reflective film layer was used.

  Next, a CsI conversion film layer (scintillator layer) having a thickness of 600 μm was formed on a glass substrate made of Corning Corporation trade name: Corning 1737. Then, the protective layer was produced by sticking the said multilayer resin film through the contact bonding layer on the glass substrate surface containing the surface and side surface of this scintillator layer.

Example 4
After mixing 80% by weight of titanium oxide powder having an average particle size of 0.2 μm and 20% by weight of butyral resin (trade name of Sekisui Chemical Co., Ltd .; ESREC BMS) together with cyclohexanone, the mixture is uniformly dispersed using a homogenizer. The coating for reflecting film was prepared in advance. Next, the reflective film coating was applied to one side of a moisture-proof layer (trade name: GX film manufactured by Toppan Printing Co., Ltd.) having a thickness of 80 μm using a bar coater and dried to form a reflective film layer having a thickness of 100 μm. did. Subsequently, a multilayered resin film having a frame-like adhesive layer by adhering a 0.7 mm thick acrylic double-sided adhesive (trade name; S-0779, manufactured by Soken Chemical Co., Ltd.) to the periphery of the surface of the reflective film layer. It was.

  Next, a CsI conversion film layer (scintillator layer) having a thickness of 600 μm was formed on a glass substrate made of Corning Corporation trade name: Corning 1737. Then, the protective layer was produced by sticking the said multilayer resin film through the frame-shaped contact bonding layer on the glass substrate surface containing the surface and side surface of this scintillator layer.

(Example 5)
After mixing 80% by weight of titanium oxide powder having an average particle size of 0.2 μm and 20% by weight of butyral resin (trade name of Sekisui Chemical Co., Ltd .; ESREC BMS) together with cyclohexanone, the mixture is uniformly dispersed using a homogenizer. The coating for reflecting film was prepared in advance. Subsequently, the coating for reflective film was applied to one side of an 80 μm thick moisture-proof layer (trade name, manufactured by Toppan Printing Co., Ltd .; GX film) using a bar coater so that the peripheral edge of the one side was exposed, dried and thickened. A reflective film layer having a thickness of 100 μm was formed. Next, after adhering a 0.7 mm thick acrylic double-sided adhesive (trade name: S-0779) to the periphery of the surface of the reflective film layer in the shape of a frame, the reflective film layer-unformed part at the periphery of the moisture-proof layer Was bent to the side surface of the frame-like adhesive layer and adhered to obtain a multilayer resin film.

  Next, a CsI conversion film layer (scintillator layer) having a thickness of 600 μm was formed on a glass substrate made of Corning Corporation trade name: Corning 1737. Then, the protective layer was produced by sticking the said multilayer resin film through the frame-shaped contact bonding layer on the glass substrate surface containing the surface and side surface of this scintillator layer. This pasting was performed in a 60 ° C. vacuum dryer.

(Comparative Example 1)
A CsI conversion film layer (scintillator layer) having a thickness of 600 μm was formed on a glass substrate made of Corning Corporation product name: Corning 1737. Subsequently, a parylene vapor-deposited film having a thickness of 40 μm is formed as a moisture-proof layer on the glass substrate surface including the surface and side surfaces of the scintillator layer, and then the end portion of the parylene vapor-deposited film is treated with a two-component curable epoxy resin. Was made.

  For Examples 1 to 5 and Comparative Example 1, the water vapor transmission rate of the protective layer, the water absorption rate of the scintillator layer, the retention rate of resolution, and the shape change accompanying the water absorption of the scintillator layer were examined by the following methods.

1. Measurement of water vapor transmission rate of protective layer About the protective layer used in Examples 1 to 5 and Comparative Example 1, a scratch, a void, a portion without breakage was selected, and a water vapor transmission rate measurement device manufactured by MOCON of the United States of America was used. The moisture permeability was calculated by measuring the amount of moisture absorption from the change in mass in a 90% humidity atmosphere.

2. Measurement of water absorption rate of scintillator layer The protective layers used in Examples 1 to 5 and Comparative Example 1 were formed on a glass substrate, and the water absorption rate after being left in an atmosphere of 60 ° C. and 90% RH for 500 hours was measured.

3. Measurement of retention rate of resolution After the structures of Examples 1 to 5 and Comparative Example 1 in which a scintillator layer on a glass substrate was formed and left in a 60 ° C., 90% RH atmosphere for 500 hours, the X-ray irradiation conditions were accelerated. How bright and dark the X-ray image is with a fine resolution chart that includes two pairs of line-and-space at a distance of 1 mm under the condition that an aluminum filter for soft X-ray removal is inserted at a voltage of 70 kV-1 mA. The contrast transfer function (Contrast Transfer Function: CTF) was measured as an index to determine whether or not the change was in the initial value.

4). SEM observation results of scintillator layer The structures of Examples 1 to 5 and Comparative Example 1 in which a protective layer was formed on a scintillator layer on a glass substrate were left in an atmosphere of 60 ° C. and 90% RH for 500 hours, and then the protective layer was removed. The shape of the scintillator layer was observed with SEM.

  These results are shown in Table 1 below.

  As apparent from Table 1, it can be seen that Examples 1 to 5 show higher moisture resistance due to the protective layer than Comparative Example 1, and show a higher resolution maintenance rate.

The principal part sectional view showing the radiation detector (X-ray detector) concerning a 1st embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a protective layer forming step in the X-ray detector of FIG. 1. The schematic sectional drawing which shows the formation process of the protective layer in the X-ray detector which concerns on 2nd Embodiment of this invention. The schematic sectional drawing which shows the formation process of the protective layer in the X-ray detector which concerns on 3rd Embodiment of this invention. The schematic sectional drawing which shows the formation process of the protective layer in the X-ray detector which concerns on 4th Embodiment of this invention. The schematic sectional drawing which shows the formation process of the protective layer in the X-ray detector which concerns on the modification of 4th Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... X-ray detector, 2 ... Light conversion board | substrate (electrode board | substrate), 3 ... Glass board | substrate (translucent board | substrate), 4 ... Thin film transistor, 5 ... Storage capacitor, 7 ... Photodiode (photoelectric conversion element), 31 ... Scintillator Layers 41... Protective layer 52. Reflective film layer 43. Adhesive layer 44. Dampproof layer 45.

Claims (5)

A transparent substrate, a plurality of thin film transistors and a plurality of storage capacitors provided on the transparent substrate, an insulating layer formed on the transparent substrate including the thin film transistors and the storage capacitors, and connected to each of the thin film transistors, and visible An electrode substrate having a plurality of photoelectric conversion elements for converting light into an electrical signal;
A scintillator layer formed on the electrode substrate for converting radiation into visible light; and a reflective film layer formed on at least the scintillator layer and containing 70% by weight or more of titanium oxide powder in a thermoplastic polymer compound; A protective layer having an adhesive layer formed on the surface of the electrode substrate including a film layer, and a moisture-proof layer adhered to the adhesive layer and having a moisture permeability of 0.5 g / m ² / day or less at 40 ° C. and 90 RH;
A radiation detector comprising: A transparent substrate, a plurality of thin film transistors and a plurality of storage capacitors provided on the transparent substrate, an insulating layer formed on the transparent substrate including the thin film transistors and the storage capacitors, and connected to each of the thin film transistors, and visible An electrode substrate having a plurality of photoelectric conversion elements for converting light into an electrical signal;
A scintillator layer formed on the electrode substrate for converting radiation into visible light; and a reflective film layer formed on at least the scintillator layer and containing 70% by weight or more of titanium oxide powder in a thermoplastic polymer compound; and the electrode substrate A frame-like adhesive layer located on the surface and the side of the scintillator layer and adhered to the reflective film layer, and adhered onto the frame-like adhesive layer, and moisture permeability at 40 ° C. and 90 RH is 0.5 g / m ² / a protective layer having a moisture-proof layer of day or less;
A radiation detector comprising: A transparent substrate, a plurality of thin film transistors and a plurality of storage capacitors provided on the transparent substrate, an insulating layer formed on the transparent substrate including the thin film transistors and the storage capacitors, and connected to each of the thin film transistors, and visible An electrode substrate having a plurality of photoelectric conversion elements for converting light into an electrical signal;
A scintillator layer that is formed on the electrode substrate and converts radiation into visible light; and an adhesive layer that is bonded to the electrode substrate including the scintillator layer; and a titanium oxide that is bonded to the adhesive layer and is formed on the thermoplastic polymer compound. A protective layer having a reflective film layer containing 70% by weight or more of a powder and a moisture-proof layer laminated on the reflective film layer and having a moisture permeability of 0.5 g / m ² / day or less at 40 ° C. and 90 RH;
A radiation detector comprising: A transparent substrate, a plurality of thin film transistors and a plurality of storage capacitors provided on the transparent substrate, an insulating layer formed on the transparent substrate including the thin film transistors and the storage capacitors, and connected to each of the thin film transistors, and visible An electrode substrate having a plurality of photoelectric conversion elements for converting light into an electrical signal;
A scintillator layer that is formed on the electrode substrate and converts radiation into visible light; and a frame-like adhesive layer that is bonded to the electrode substrate surface and the side surface of the scintillator layer; A reflective film layer containing 70% by weight or more of titanium oxide powder in a polymer compound; a moisture-proof layer laminated on the reflective film layer and having a moisture permeability of 0.5 g / m ² / day or less at 40 ° C. and 90 RH; A protective layer having
A radiation detector comprising:   The radiation detector according to any one of claims 1 to 4, wherein the adhesive layer is an acrylic pressure-sensitive adhesive layer, a silicone pressure-sensitive adhesive layer, or a butyl rubber-based pressure-sensitive adhesive layer that exhibits adhesiveness at room temperature.

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